Re: Performance Characteristics of All Linux RAIDs (mdadm/bonnie++)

[Justin Piszcz <jpiszcz@lucidpixels.com>]

On Thu, 29 May 2008, Holger Kiehl wrote:

> On Wed, 28 May 2008, Justin Piszcz wrote:
>
>> Hardware:
>> 
>> 1. Utilized (6) 400 gigabyte sata hard drives.
>> 2. Everything is on PCI-e (965 chipset & a 2port sata card)
>> 
>> Used the following 'optimizations' for all tests.
>> 
>> # Set read-ahead.
>> echo "Setting read-ahead to 64 MiB for /dev/md3"
>> blockdev --setra 65536 /dev/md3
>> 
>> # Set stripe-cache_size for RAID5.
>> echo "Setting stripe_cache_size to 16 MiB for /dev/md3"
>> echo 16384 > /sys/block/md3/md/stripe_cache_size
>> 
>> # Disable NCQ on all disks.
>> echo "Disabling NCQ on all disks..."
>> for i in $DISKS
>> do
>>  echo "Disabling NCQ on $i"
>>  echo 1 > /sys/block/"$i"/device/queue_depth
>> done
>> 
>> Software:
>> 
>> Kernel: 2.6.23.1 x86_64
>> Filesystem: XFS
>> Mount options: defaults,noatime
>> 
>> Results:
>> 
>> http://home.comcast.net/~jpiszcz/raid/20080528/raid-levels.html
>> http://home.comcast.net/~jpiszcz/raid/20080528/raid-levels.txt
>> 
> Why is the Sequential Output (Block) for raid6 165719 and for raid5 only
> 86797? I would have thought that raid6 was always a bit slower in writting
> due to having to write double amount of parity data.
>
> Holger
>

RAID5 (2nd test of 3 averaged runs) & Single disk added:
http://home.comcast.net/~jpiszcz/raid/20080528/raid-levels.html